aboutsummaryrefslogtreecommitdiffstats
path: root/src/core/SkScalerContext.cpp
blob: eee0dc5fcee6b85f9821e9ae147c475ffb5ddb2a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782

/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */


#include "SkScalerContext.h"
#include "SkColorPriv.h"
#include "SkDescriptor.h"
#include "SkDraw.h"
#include "SkFontHost.h"
#include "SkMaskFilter.h"
#include "SkPathEffect.h"
#include "SkRasterizer.h"
#include "SkRasterClip.h"
#include "SkStroke.h"
#include "SkThread.h"

#define ComputeBWRowBytes(width)        (((unsigned)(width) + 7) >> 3)

void SkGlyph::toMask(SkMask* mask) const {
    SkASSERT(mask);

    mask->fImage = (uint8_t*)fImage;
    mask->fBounds.set(fLeft, fTop, fLeft + fWidth, fTop + fHeight);
    mask->fRowBytes = this->rowBytes();
    mask->fFormat = static_cast<SkMask::Format>(fMaskFormat);
}

size_t SkGlyph::computeImageSize() const {
    const size_t size = this->rowBytes() * fHeight;

    switch (fMaskFormat) {
        case SkMask::k3D_Format:
            return 3 * size;
        default:
            return size;
    }
}

void SkGlyph::zeroMetrics() {
    fAdvanceX = 0;
    fAdvanceY = 0;
    fWidth    = 0;
    fHeight   = 0;
    fTop      = 0;
    fLeft     = 0;
    fRsbDelta = 0;
    fLsbDelta = 0;
}

///////////////////////////////////////////////////////////////////////////////

#ifdef SK_DEBUG
    #define DUMP_RECx
#endif

static SkFlattenable* load_flattenable(const SkDescriptor* desc, uint32_t tag) {
    SkFlattenable*  obj = NULL;
    uint32_t        len;
    const void*     data = desc->findEntry(tag, &len);

    if (data) {
        SkFlattenableReadBuffer   buffer(data, len);
        obj = buffer.readFlattenable();
        SkASSERT(buffer.offset() == buffer.size());
    }
    return obj;
}

SkScalerContext::SkScalerContext(const SkDescriptor* desc)
    : fPathEffect(NULL), fMaskFilter(NULL)
{
    fBaseGlyphCount = 0;
    fNextContext = NULL;

    const Rec* rec = (const Rec*)desc->findEntry(kRec_SkDescriptorTag, NULL);
    SkASSERT(rec);

    fRec = *rec;

#ifdef DUMP_REC
    desc->assertChecksum();
    SkDebugf("SkScalarContext checksum %x count %d length %d\n",
             desc->getChecksum(), desc->getCount(), desc->getLength());
    SkDebugf(" textsize %g prescale %g preskew %g post [%g %g %g %g]\n",
        rec->fTextSize, rec->fPreScaleX, rec->fPreSkewX, rec->fPost2x2[0][0],
        rec->fPost2x2[0][1], rec->fPost2x2[1][0], rec->fPost2x2[1][1]);
    SkDebugf("  frame %g miter %g hints %d framefill %d format %d join %d\n",
        rec->fFrameWidth, rec->fMiterLimit, rec->fHints, rec->fFrameAndFill,
        rec->fMaskFormat, rec->fStrokeJoin);
    SkDebugf("  pathEffect %x maskFilter %x\n",
             desc->findEntry(kPathEffect_SkDescriptorTag, NULL),
        desc->findEntry(kMaskFilter_SkDescriptorTag, NULL));
#endif

    fPathEffect = (SkPathEffect*)load_flattenable(desc, kPathEffect_SkDescriptorTag);
    fMaskFilter = (SkMaskFilter*)load_flattenable(desc, kMaskFilter_SkDescriptorTag);
    fRasterizer = (SkRasterizer*)load_flattenable(desc, kRasterizer_SkDescriptorTag);

    // initialize based on our settings. subclasses can also force this
    fGenerateImageFromPath = fRec.fFrameWidth > 0 || fPathEffect != NULL ||
                             fRasterizer != NULL;
}

SkScalerContext::~SkScalerContext() {
    SkDELETE(fNextContext);

    SkSafeUnref(fPathEffect);
    SkSafeUnref(fMaskFilter);
    SkSafeUnref(fRasterizer);
}

static SkScalerContext* allocNextContext(const SkScalerContext::Rec& rec) {
    // fonthost will determine the next possible font to search, based
    // on the current font in fRec. It will return NULL if ctx is our
    // last font that can be searched (i.e. ultimate fallback font)
#ifdef SK_BUILD_FOR_ANDROID
        // On Android, pass entire rec structure so that clients can change fallback behavior
        uint32_t newFontID = SkFontHost::NextLogicalFont(rec);
#else
        uint32_t newFontID = SkFontHost::NextLogicalFont(rec.fFontID, rec.fOrigFontID);
#endif

    if (0 == newFontID) {
        return NULL;
    }

    SkAutoDescriptor    ad(sizeof(rec) + SkDescriptor::ComputeOverhead(1));
    SkDescriptor*       desc = ad.getDesc();

    desc->init();
    SkScalerContext::Rec* newRec =
    (SkScalerContext::Rec*)desc->addEntry(kRec_SkDescriptorTag,
                                          sizeof(rec), &rec);
    newRec->fFontID = newFontID;
    desc->computeChecksum();

    return SkFontHost::CreateScalerContext(desc);
}

/*  Return the next context, creating it if its not already created, but return
    NULL if the fonthost says there are no more fonts to fallback to.
 */
SkScalerContext* SkScalerContext::getNextContext() {
    SkScalerContext* next = fNextContext;
    // if next is null, then either it isn't cached yet, or we're at the
    // end of our possible chain
    if (NULL == next) {
        next = allocNextContext(fRec);
        if (NULL == next) {
            return NULL;
        }
        // next's base is our base + our local count
        next->setBaseGlyphCount(fBaseGlyphCount + this->getGlyphCount());
        // cache the answer
        fNextContext = next;
    }
    return next;
}

SkScalerContext* SkScalerContext::getContextFromChar(SkUnichar uni, unsigned& glyphID) {
    SkScalerContext* ctx = this;
    for (;;) {
        glyphID = ctx->generateCharToGlyph(uni);
        if (glyphID) {
            break;  // found it
        }
        ctx = ctx->getNextContext();
        if (NULL == ctx) {
            return NULL;
        }
    }
    return ctx;
}

SkScalerContext* SkScalerContext::getGlyphContext(const SkGlyph& glyph) {
    unsigned glyphID = glyph.getGlyphID();
    SkScalerContext* ctx = this;
    for (;;) {
        unsigned count = ctx->getGlyphCount();
        if (glyphID < count) {
            break;
        }
        glyphID -= count;
        ctx = ctx->getNextContext();
        if (NULL == ctx) {
            SkDebugf("--- no context for glyph %x\n", glyph.getGlyphID());
            // just return the original context (this)
            return this;
        }
    }
    return ctx;
}

#ifdef SK_BUILD_FOR_ANDROID
SkFontID SkScalerContext::findTypefaceIdForChar(SkUnichar uni) {
    unsigned glyphID;
    SkScalerContext* ctx = getContextFromChar(uni, glyphID);
    if (ctx) {
        return ctx->fRec.fFontID;
    } else {
        return 0;
    }
}

/*  This loops through all available fallback contexts (if needed) until it
    finds some context that can handle the unichar and return it.

    As this is somewhat expensive operation, it should only be done on the first
    char of a run.
 */
unsigned SkScalerContext::getBaseGlyphCount(SkUnichar uni) {
    unsigned glyphID;
    SkScalerContext* ctx = getContextFromChar(uni, glyphID);
    if (ctx) {
        return ctx->fBaseGlyphCount;
    } else {
        SkDEBUGF(("--- no context for char %x\n", uni));
        return this->fBaseGlyphCount;
    }
}
#endif

/*  This loops through all available fallback contexts (if needed) until it
    finds some context that can handle the unichar. If all fail, returns 0
 */
uint16_t SkScalerContext::charToGlyphID(SkUnichar uni) {

    unsigned glyphID;
    SkScalerContext* ctx = getContextFromChar(uni, glyphID);
    if (!ctx) {
        return 0; // no more contexts, return missing glyph
    }
    // add the ctx's base, making glyphID unique for chain of contexts
    glyphID += ctx->fBaseGlyphCount;
    // check for overflow of 16bits, since our glyphID cannot exceed that
    if (glyphID > 0xFFFF) {
        glyphID = 0;
    }
    return SkToU16(glyphID);
}

SkUnichar SkScalerContext::glyphIDToChar(uint16_t glyphID) {
    SkScalerContext* ctx = this;
    unsigned rangeEnd = 0;
    do {
        unsigned rangeStart = rangeEnd;

        rangeEnd += ctx->getGlyphCount();
        if (rangeStart <= glyphID && glyphID < rangeEnd) {
            return ctx->generateGlyphToChar(glyphID - rangeStart);
        }
        ctx = ctx->getNextContext();
    } while (NULL != ctx);
    return 0;
}

void SkScalerContext::getAdvance(SkGlyph* glyph) {
    // mark us as just having a valid advance
    glyph->fMaskFormat = MASK_FORMAT_JUST_ADVANCE;
    // we mark the format before making the call, in case the impl
    // internally ends up calling its generateMetrics, which is OK
    // albeit slower than strictly necessary
    this->getGlyphContext(*glyph)->generateAdvance(glyph);
}

void SkScalerContext::getMetrics(SkGlyph* glyph) {
    this->getGlyphContext(*glyph)->generateMetrics(glyph);

    // for now we have separate cache entries for devkerning on and off
    // in the future we might share caches, but make our measure/draw
    // code make the distinction. Thus we zap the values if the caller
    // has not asked for them.
    if ((fRec.fFlags & SkScalerContext::kDevKernText_Flag) == 0) {
        // no devkern, so zap the fields
        glyph->fLsbDelta = glyph->fRsbDelta = 0;
    }

    // if either dimension is empty, zap the image bounds of the glyph
    if (0 == glyph->fWidth || 0 == glyph->fHeight) {
        glyph->fWidth   = 0;
        glyph->fHeight  = 0;
        glyph->fTop     = 0;
        glyph->fLeft    = 0;
        glyph->fMaskFormat = 0;
        return;
    }

    if (fGenerateImageFromPath) {
        SkPath      devPath, fillPath;
        SkMatrix    fillToDevMatrix;

        this->internalGetPath(*glyph, &fillPath, &devPath, &fillToDevMatrix);

        if (fRasterizer) {
            SkMask  mask;

            if (fRasterizer->rasterize(fillPath, fillToDevMatrix, NULL,
                                       fMaskFilter, &mask,
                                       SkMask::kJustComputeBounds_CreateMode)) {
                glyph->fLeft    = mask.fBounds.fLeft;
                glyph->fTop     = mask.fBounds.fTop;
                glyph->fWidth   = SkToU16(mask.fBounds.width());
                glyph->fHeight  = SkToU16(mask.fBounds.height());
            } else {
                goto SK_ERROR;
            }
        } else {
            // just use devPath
            SkIRect ir;
            devPath.getBounds().roundOut(&ir);

            if (ir.isEmpty() || !ir.is16Bit()) {
                goto SK_ERROR;
            }
            glyph->fLeft    = ir.fLeft;
            glyph->fTop     = ir.fTop;
            glyph->fWidth   = SkToU16(ir.width());
            glyph->fHeight  = SkToU16(ir.height());
        }
    }

	if (SkMask::kARGB32_Format != glyph->fMaskFormat) {
		glyph->fMaskFormat = fRec.fMaskFormat;
	}

    if (fMaskFilter) {
        SkMask      src, dst;
        SkMatrix    matrix;

        glyph->toMask(&src);
        fRec.getMatrixFrom2x2(&matrix);

        src.fImage = NULL;  // only want the bounds from the filter
        if (fMaskFilter->filterMask(&dst, src, matrix, NULL)) {
            SkASSERT(dst.fImage == NULL);
            glyph->fLeft    = dst.fBounds.fLeft;
            glyph->fTop     = dst.fBounds.fTop;
            glyph->fWidth   = SkToU16(dst.fBounds.width());
            glyph->fHeight  = SkToU16(dst.fBounds.height());
            glyph->fMaskFormat = dst.fFormat;
        }
    }
    return;

SK_ERROR:
    // draw nothing 'cause we failed
    glyph->fLeft    = 0;
    glyph->fTop     = 0;
    glyph->fWidth   = 0;
    glyph->fHeight  = 0;
    // put a valid value here, in case it was earlier set to
    // MASK_FORMAT_JUST_ADVANCE
    glyph->fMaskFormat = fRec.fMaskFormat;
}

static bool isLCD(const SkScalerContext::Rec& rec) {
    return SkMask::kLCD16_Format == rec.fMaskFormat ||
           SkMask::kLCD32_Format == rec.fMaskFormat;
}

static uint16_t a8_to_rgb565(unsigned a8) {
    return SkPackRGB16(a8 >> 3, a8 >> 2, a8 >> 3);
}

static void copyToLCD16(const SkBitmap& src, const SkMask& dst) {
    SkASSERT(SkBitmap::kA8_Config == src.config());
    SkASSERT(SkMask::kLCD16_Format == dst.fFormat);

    const int width = dst.fBounds.width();
    const int height = dst.fBounds.height();
    const uint8_t* srcP = src.getAddr8(0, 0);
    size_t srcRB = src.rowBytes();
    uint16_t* dstP = (uint16_t*)dst.fImage;
    size_t dstRB = dst.fRowBytes;
    for (int y = 0; y < height; ++y) {
        for (int x = 0; x < width; ++x) {
            dstP[x] = a8_to_rgb565(srcP[x]);
        }
        srcP += srcRB;
        dstP = (uint16_t*)((char*)dstP + dstRB);
    }
}

#define SK_FREETYPE_LCD_LERP    160

static int lerp(int start, int end) {
    SkASSERT((unsigned)SK_FREETYPE_LCD_LERP <= 256);
    return start + ((end - start) * (SK_FREETYPE_LCD_LERP) >> 8);
}

static uint16_t packLCD16(unsigned r, unsigned g, unsigned b) {
    if (SK_FREETYPE_LCD_LERP) {
        // want (a+b+c)/3, but we approx to avoid the divide
        unsigned ave = (5 * (r + g + b) + g) >> 4;
        r = lerp(r, ave);
        g = lerp(g, ave);
        b = lerp(b, ave);
    }
    return SkPackRGB16(r >> 3, g >> 2, b >> 3);
}

static void pack3xHToLCD16(const SkBitmap& src, const SkMask& dst) {
    SkASSERT(SkBitmap::kA8_Config == src.config());
    SkASSERT(SkMask::kLCD16_Format == dst.fFormat);
    
    const int width = dst.fBounds.width();
    const int height = dst.fBounds.height();
    uint16_t* dstP = (uint16_t*)dst.fImage;
    size_t dstRB = dst.fRowBytes;
    for (int y = 0; y < height; ++y) {
        const uint8_t* srcP = src.getAddr8(0, y);
        for (int x = 0; x < width; ++x) {
            unsigned r = *srcP++;
            unsigned g = *srcP++;
            unsigned b = *srcP++;
            dstP[x] = packLCD16(r, g, b);
        }
        dstP = (uint16_t*)((char*)dstP + dstRB);
    }
}

static void pack3xHToLCD32(const SkBitmap& src, const SkMask& dst) {
    SkASSERT(SkBitmap::kA8_Config == src.config());
    SkASSERT(SkMask::kLCD32_Format == dst.fFormat);
    
    const int width = dst.fBounds.width();
    const int height = dst.fBounds.height();
    SkPMColor* dstP = (SkPMColor*)dst.fImage;
    size_t dstRB = dst.fRowBytes;
    for (int y = 0; y < height; ++y) {
        const uint8_t* srcP = src.getAddr8(0, y);
        for (int x = 0; x < width; ++x) {
            unsigned r = *srcP++;
            unsigned g = *srcP++;
            unsigned b = *srcP++;
            unsigned a = SkMax32(SkMax32(r, g), b);
            dstP[x] = SkPackARGB32(a, r, g, b);
        }
        dstP = (SkPMColor*)((char*)dstP + dstRB);
    }
}

static void generateMask(const SkMask& mask, const SkPath& path) {
    SkBitmap::Config config;
    SkPaint     paint;

    int srcW = mask.fBounds.width();
    int srcH = mask.fBounds.height();
    int dstW = srcW;
    int dstH = srcH;
    int dstRB = mask.fRowBytes;

    SkMatrix matrix;
    matrix.setTranslate(-SkIntToScalar(mask.fBounds.fLeft),
                        -SkIntToScalar(mask.fBounds.fTop));

    if (SkMask::kBW_Format == mask.fFormat) {
        config = SkBitmap::kA1_Config;
        paint.setAntiAlias(false);
    } else {
        config = SkBitmap::kA8_Config;
        paint.setAntiAlias(true);
        switch (mask.fFormat) {
            case SkMask::kA8_Format:
                break;
            case SkMask::kLCD16_Format:
            case SkMask::kLCD32_Format:
                // TODO: trigger off LCD orientation
                dstW *= 3;
                matrix.postScale(SkIntToScalar(3), SK_Scalar1);
                dstRB = 0;  // signals we need a copy
                break;
            default:
                SkDEBUGFAIL("unexpected mask format");
        }
    }

    SkRasterClip clip;
    clip.setRect(SkIRect::MakeWH(dstW, dstH));

    SkBitmap bm;
    bm.setConfig(config, dstW, dstH, dstRB);

    if (0 == dstRB) {
        bm.allocPixels();
        bm.lockPixels();
    } else {
        bm.setPixels(mask.fImage);
    }
    sk_bzero(bm.getPixels(), bm.getSafeSize());
    
    SkDraw  draw;
    sk_bzero(&draw, sizeof(draw));
    draw.fRC    = &clip;
    draw.fClip  = &clip.bwRgn();
    draw.fMatrix = &matrix;
    draw.fBitmap = &bm;
    draw.drawPath(path, paint);
    
    if (0 == dstRB) {
        switch (mask.fFormat) {
            case SkMask::kLCD16_Format:
                pack3xHToLCD16(bm, mask);
                break;
            case SkMask::kLCD32_Format:
                pack3xHToLCD32(bm, mask);
                break;
            default:
                SkDEBUGFAIL("bad format for copyback");
        }
    }
}

void SkScalerContext::getImage(const SkGlyph& origGlyph) {
    const SkGlyph*  glyph = &origGlyph;
    SkGlyph         tmpGlyph;

    if (fMaskFilter) {   // restore the prefilter bounds
        tmpGlyph.init(origGlyph.fID);

        // need the original bounds, sans our maskfilter
        SkMaskFilter* mf = fMaskFilter;
        fMaskFilter = NULL;             // temp disable
        this->getMetrics(&tmpGlyph);
        fMaskFilter = mf;               // restore

        tmpGlyph.fImage = origGlyph.fImage;

        // we need the prefilter bounds to be <= filter bounds
        SkASSERT(tmpGlyph.fWidth <= origGlyph.fWidth);
        SkASSERT(tmpGlyph.fHeight <= origGlyph.fHeight);
        glyph = &tmpGlyph;
    }

    if (fGenerateImageFromPath) {
        SkPath      devPath, fillPath;
        SkMatrix    fillToDevMatrix;
        SkMask      mask;

        this->internalGetPath(*glyph, &fillPath, &devPath, &fillToDevMatrix);
        glyph->toMask(&mask);

        if (fRasterizer) {
            mask.fFormat = SkMask::kA8_Format;
            sk_bzero(glyph->fImage, mask.computeImageSize());

            if (!fRasterizer->rasterize(fillPath, fillToDevMatrix, NULL,
                                        fMaskFilter, &mask,
                                        SkMask::kJustRenderImage_CreateMode)) {
                return;
            }
        } else {
            generateMask(mask, devPath);
        }
    } else {
        this->getGlyphContext(*glyph)->generateImage(*glyph);
    }

    if (fMaskFilter) {
        SkMask      srcM, dstM;
        SkMatrix    matrix;

        // the src glyph image shouldn't be 3D
        SkASSERT(SkMask::k3D_Format != glyph->fMaskFormat);
        glyph->toMask(&srcM);
        fRec.getMatrixFrom2x2(&matrix);

        if (fMaskFilter->filterMask(&dstM, srcM, matrix, NULL)) {
            int width = SkFastMin32(origGlyph.fWidth, dstM.fBounds.width());
            int height = SkFastMin32(origGlyph.fHeight, dstM.fBounds.height());
            int dstRB = origGlyph.rowBytes();
            int srcRB = dstM.fRowBytes;

            const uint8_t* src = (const uint8_t*)dstM.fImage;
            uint8_t* dst = (uint8_t*)origGlyph.fImage;

            if (SkMask::k3D_Format == dstM.fFormat) {
                // we have to copy 3 times as much
                height *= 3;
            }

            // clean out our glyph, since it may be larger than dstM
            //sk_bzero(dst, height * dstRB);

            while (--height >= 0) {
                memcpy(dst, src, width);
                src += srcRB;
                dst += dstRB;
            }
            SkMask::FreeImage(dstM.fImage);
        }
    }
}

void SkScalerContext::getPath(const SkGlyph& glyph, SkPath* path) {
    this->internalGetPath(glyph, NULL, path, NULL);
}

void SkScalerContext::getFontMetrics(SkPaint::FontMetrics* mx,
                                     SkPaint::FontMetrics* my) {
    this->generateFontMetrics(mx, my);
}

SkUnichar SkScalerContext::generateGlyphToChar(uint16_t glyph) {
    return 0;
}

///////////////////////////////////////////////////////////////////////////////

void SkScalerContext::internalGetPath(const SkGlyph& glyph, SkPath* fillPath,
                                  SkPath* devPath, SkMatrix* fillToDevMatrix) {
    SkPath  path;

    this->getGlyphContext(glyph)->generatePath(glyph, &path);

    if (fRec.fFlags & SkScalerContext::kSubpixelPositioning_Flag) {
        SkFixed dx = glyph.getSubXFixed();
        SkFixed dy = glyph.getSubYFixed();
        if (dx | dy) {
            path.offset(SkFixedToScalar(dx), SkFixedToScalar(dy));
        }
    }

    if (fRec.fFrameWidth > 0 || fPathEffect != NULL) {
        // need the path in user-space, with only the point-size applied
        // so that our stroking and effects will operate the same way they
        // would if the user had extracted the path themself, and then
        // called drawPath
        SkPath      localPath;
        SkMatrix    matrix, inverse;

        fRec.getMatrixFrom2x2(&matrix);
        matrix.invert(&inverse);
        path.transform(inverse, &localPath);
        // now localPath is only affected by the paint settings, and not the canvas matrix

        SkScalar width = fRec.fFrameWidth;

        if (fPathEffect) {
            SkPath effectPath;

            if (fPathEffect->filterPath(&effectPath, localPath, &width)) {
                localPath.swap(effectPath);
            }
        }

        if (width > 0) {
            SkStroke    stroker;
            SkPath      outline;

            stroker.setWidth(width);
            stroker.setMiterLimit(fRec.fMiterLimit);
            stroker.setJoin((SkPaint::Join)fRec.fStrokeJoin);
            stroker.setDoFill(SkToBool(fRec.fFlags & kFrameAndFill_Flag));
            stroker.strokePath(localPath, &outline);
            localPath.swap(outline);
        }

        // now return stuff to the caller
        if (fillToDevMatrix) {
            *fillToDevMatrix = matrix;
        }
        if (devPath) {
            localPath.transform(matrix, devPath);
        }
        if (fillPath) {
            fillPath->swap(localPath);
        }
    } else {   // nothing tricky to do
        if (fillToDevMatrix) {
            fillToDevMatrix->reset();
        }
        if (devPath) {
            if (fillPath == NULL) {
                devPath->swap(path);
            } else {
                *devPath = path;
            }
        }

        if (fillPath) {
            fillPath->swap(path);
        }
    }

    if (devPath) {
        devPath->updateBoundsCache();
    }
    if (fillPath) {
        fillPath->updateBoundsCache();
    }
}


void SkScalerContext::Rec::getMatrixFrom2x2(SkMatrix* dst) const {
    dst->reset();
    dst->setScaleX(fPost2x2[0][0]);
    dst->setSkewX( fPost2x2[0][1]);
    dst->setSkewY( fPost2x2[1][0]);
    dst->setScaleY(fPost2x2[1][1]);
}

void SkScalerContext::Rec::getLocalMatrix(SkMatrix* m) const {
    m->setScale(SkScalarMul(fTextSize, fPreScaleX), fTextSize);
    if (fPreSkewX) {
        m->postSkew(fPreSkewX, 0);
    }
}

void SkScalerContext::Rec::getSingleMatrix(SkMatrix* m) const {
    this->getLocalMatrix(m);

    //  now concat the device matrix
    SkMatrix    deviceMatrix;
    this->getMatrixFrom2x2(&deviceMatrix);
    m->postConcat(deviceMatrix);
}

SkAxisAlignment SkComputeAxisAlignmentForHText(const SkMatrix& matrix) {
    SkASSERT(!matrix.hasPerspective());
    
    if (0 == matrix[SkMatrix::kMSkewY]) {
        return kX_SkAxisAlignment;
    }
    if (0 == matrix[SkMatrix::kMScaleX]) {
        return kY_SkAxisAlignment;
    }
    return kNone_SkAxisAlignment;
}

///////////////////////////////////////////////////////////////////////////////

#include "SkFontHost.h"

class SkScalerContext_Empty : public SkScalerContext {
public:
    SkScalerContext_Empty(const SkDescriptor* desc) : SkScalerContext(desc) {}

protected:
    virtual unsigned generateGlyphCount() {
        return 0;
    }
    virtual uint16_t generateCharToGlyph(SkUnichar uni) {
        return 0;
    }
    virtual void generateAdvance(SkGlyph* glyph) {
        glyph->zeroMetrics();
    }
    virtual void generateMetrics(SkGlyph* glyph) {
        glyph->zeroMetrics();
    }
    virtual void generateImage(const SkGlyph& glyph) {}
    virtual void generatePath(const SkGlyph& glyph, SkPath* path) {}
    virtual void generateFontMetrics(SkPaint::FontMetrics* mx,
                                     SkPaint::FontMetrics* my) {
        if (mx) {
            sk_bzero(mx, sizeof(*mx));
        }
        if (my) {
            sk_bzero(my, sizeof(*my));
        }
    }
};

extern SkScalerContext* SkCreateColorScalerContext(const SkDescriptor* desc);

SkScalerContext* SkScalerContext::Create(const SkDescriptor* desc) {
	SkScalerContext* c = NULL;  //SkCreateColorScalerContext(desc);
	if (NULL == c) {
		c = SkFontHost::CreateScalerContext(desc);
	}
    if (NULL == c) {
        c = SkNEW_ARGS(SkScalerContext_Empty, (desc));
    }
    return c;
}